Juha Niinikoski

Clinical Hyperbaric Oxygen Therapy, Wound Perfusion, and Transcutaneous Oximetry

Hyperbaric oxygen therapy (HBOT) is an important adjunct in the management of problem wounds which exist in chronic oxygen deficiency and in which the local oxygen tension is below optimal for healing. In the treatment of hypoxic and ischemic wounds, the most important effects of hyperbaric oxygenation are the stimulation of fibroblast proliferation and differentiation, increased collagen formation and cross-linking, augmented neovascularization, and the stimulation of leukocyte microbial killing. Ischemic soft tissues also benefit from hyperoxygenation through improved preservation of energy metabolism and reduction of edema. Hyperbaric oxygen is administered in either a multiplace or a monoplace hyperbaric chamber. Normally, pressures of 2 to 2.5 ATA are used for a period of 90 minutes once or twice daily. For an objective assessment of wound perfusion and oxygenation, transcutaneous oximetry provides a simple, reliable, noninvasive, diagnostic technique. It can be used for assessment of tissue perfusion in the vicinity of the problem wound. Transcutaneous oximetry may be used in the assessment of wound healing potential, selection of amputation level, and patient selection for HBOT. In diabetic patients with chronic foot ulcers peri-wound transcutaneous oxygen tensions (TcPo 2) over 400 mmHg in 2.5 ATA hyperbaric oxygen or over 50 mmHg in normobaric pure oxygen predict healing success with adjuncted HBOT with high accuracy.

Effects of homodimeric isoforms of platelet-derived growth factor (PDGF-AA and PDGF-BB) on wound healing in rat.

Platelet-derived growth factor (PDGF) has been suggested to have a significant role in wound healing. The present work was aimed at studying the effects of PDGF-AA and PDGF-BB homodimers on developing granulation tissue in rats. Subcutaneously implanted hollow cylindrical cellulose sponges were used as an inductive matrix for the ingrowth of granulation tissue. Fifty microliters of solutions containing 0, 5, 50, or 500 ng of PDGF-AA or PDGF-BB homodimers was injected daily into the sponges; 7 days after implantation the granulation tissue in the sponge cylinders was analyzed. Five hundred nanograms of PDGF-BB stimulated significantly the accumulation of collagen, indicated by the elevated hydroxyproline content of the sponge (+34%, P < 0.001). Similarly, the amounts of RNA-ribose, nitrogen, hexosamines, and uronic acids were significantly higher, reflecting a PDGF-BB-induced increase in the accumulation of RNA, protein, and glycosaminoglycans. Analyses of wound fluid showed no essential changes in the composition of different cell types after PDGF-BB-treatment. The PDGF-AA-treatment increased significantly the mean amount of RNA but there were no significant changes in other parameters. In vitro both PDGF-AA and PDGF-BB increased significantly the number of rat granulation tissue derived fibroblasts in culture at concentrations of 10 and 30 ng/ml. This proliferative effect resulted in a lowered level of protein synthesis per cell. To conclude, PDGF-BB accelerates granulation tissue formation both in vitro and in vivo, whereas PDGF-AA is effective in vitro but it is clearly less effective in vivo.

Hyperbaric oxygen therapy of diabetic foot ulcers, transcutaneous oxymetry in clinical decision making

The foot ulcer is one of most common and devastating complications of diabetes and is associated with considerable morbidity and mortality. The major causes of these ulcers are ischemia/hypoxia, neuropathy, and infection, and they often coexist. Despite conventional therapy including revascularization procedures when appropriate, three situations lead frequently to amputation: persistent critical limb ischemia, soft tissue infection, and impaired wound healing from osteomyelitis. In these conditions, hyperbaric oxygen therapy may be used as an adjunctive treatment and is associated with a better outcome. Randomized, prospective, controlled trails have shown the benefit of hyperbaric oxygen therapy in diabetic ulcers of the lower extremity. Transcutaneous oxygen measurement performed under hyperbaric oxygen therapy has a prognostic significance when used to select patients who are the most likely to benefit from therapy. Hyperbaric oxygen should be added to conventional treatment if the transcutaneous oxygen tension close to the trophic lesion in 2.5 ATA hyperbaric oxygen is over 200 mmHg. Peri‐wound transcutaneous oxygen tensions over 400 mmHg in 2.5 ATA hyperbaric oxygen or over 50 mmHg in normobaric pure oxygen predict healing success with adjuncted hyperbaric oxygen therapy with high accuracy. (WOUND REP REG 2003;11:458–461)

Inflammatory Reaction and Blood Flow in Experimental Wounds Inoculated with Staphylococcus aureus

Wound healing and granulation tissue formation can be accelerated by inoculation with live pathogenic microorganisms. For further elucidation of this phenomenon the present work was undertaken to study the effects of Staphylococcus aureus microorganisms on the inflammatory reaction and blood flow in developing granulation tissue in rats. Cylindrical hollow sponge implants were used as an inductive matrix for the growth of granulation tissue. In control animals 1 ml of wound fluid was withdrawn from the central dead space of the implant immediately after implantation and replaced with 1 ml of physiological saline. In experimental animals the implants were injected with live staphylococci, 10(2) or 10(5) microorganisms/ml. Wound fluid was analyzed 3, 7, 10 and 14 days after implantation, whereas measurements of local blood flow and albumin extravasation in the granulation tissue were made after 7 days. Implants inoculated with 10(5) organisms developed infection with pus formation while implants contaminated with 10(2) organisms showed no infection. In wound fluid specimens collected from the infected implants correlation between the number of polymorphonuclear leukocytes and prostaglandin E2 concentration was statistically significant. The most prominent finding in contaminated but uninfected implants was an enhanced local blood flow. This may explain some of the mechanisms leading to S. aureus-induced acceleration of wound healing.

Oxygen Transport to Tissue under Normovolemic Moderate and Extreme Hemodilution during Coronary Bypass Operation

Oxygen transport to tissue was studied in 12 patients undergoing coronary bypass operation under normovolemic moderate and extreme hemodilution. Normovolemic moderate hemodilution (15 ml per kilogram of body weight), carried out immediately after induction of anesthesia, decreased the mean hematocrit from 0.43 to 0.33. Simultaneously, the cardiac index and the left ventricular filling pressure increased slightly but the systemic oxygen transport was reduced by 20%. The subcutaneous tissue oxygen tension (PO2) was approximately 40 mm Hg after induction of anesthesia and underwent a transient increase during moderate hemodilution. During cardiopulmonary bypass and extreme hemodilution, the mean hematocrit declined to 0.16. Concurrently, the mean tissue PO2 fell sharply and reached a minimum of 14 mm Hg at deepest hypothermia. After decannulation and reinfusion of autologous blood, the PO2 rose to 30 mm Hg. In general, total-body oxygen consumption changed along with tissue PO2. Blood lactate concentration underwent a clear increase in the early phase of extracorporeal circulation and remained rather stationary thereafter. No perioperative myocardial infarctions were encountered, and each patient made an uneventful recovery.

Alcohol abuse: A risk factor for surgical wound infections?

BACKGROUND The incidence of postoperative surgical site infections (SSIs) is difficult to estimate because of the current trend of early discharge after surgery. Both operation-related and host factors should be taken into consideration in the prevention of SSIs. We wanted to determine the actual incidence of SSIs and evaluate the risk factors in our clinic, using an extended follow-up period of 30 days after operations. METHODS We performed a prospective follow-up survey of SSIs over a 3.5-month period including a 1-month follow-up after discharge with written instructions and a telephone survey. The SSIs were defined according to Centers for Disease Control and Prevention criteria. Forty-three patient parameters were recorded, and risk factors for SSI were sought and tested by using multiple logistic regression analysis. RESULTS The follow-up was completed in 772 of 807 patients. The SSI rates in these patients were 5.3% in clean, 7.1% in clean-contaminated, 6.2% in contaminated, and 28.1% in dirty operations. Seventy-one percent of infections were not diagnosed until after discharge from the hospital. According to multiple logistic regression analysis, alcohol abuse (p < 0.0001), wound contamination class (p < 0.05), and operation duration of over 2 hours (p < 0.05) were independently significant risk factors for SSI. CONCLUSIONS A major portion of SSIs are found only after follow-up is extended during the postdischarge period. Alcohol abuse is a significant risk factor for SSI and should be taken into account when determining the susceptibility of an individual patient.

Epidermal growth factor (EGF) prevents methylprednisolone-induced inhibition of wound healing

Subcutaneously implanted cylindrical hollow viscose cellulose sponges were used to study the effect of locally applied epidermal growth factor (EGF) on methylprednisolone-induced inhibition of granulation tissue formation in rats. In in vivo studies the sponges were treated immediately after implantation with a single injection of 2 mg (approximately 1.7 x 10(-3) M) of depot methylprednisolone or with its carrier solution only. Thereafter the implants were injected daily with 5 micrograms of EGF or with its carrier solution 0.1% albumin for 7 days. Methylprednisolone treatment decreased the accumulation of nucleic acids, collagen, and glycosaminoglycans in the developing granulation tissue. After daily injections of EGF the concentrations of these tissue components returned close to the control values. In cultures of rat granulation tissue fibroblasts, 10(-4) M and 10(-3)M methylprednisolone decreased collagen synthesis by 41 and 81% from the control level, respectively. In the presence of methylprednisolone EGF treatment could not increase collagen synthesis of fibroblasts. Methylprednisolone treatment resulted in a dose-dependent reduction in pro alpha 1(I) collagen mRNA levels, which was partially inhibited by low EGF concentrations (1 and 10 ng/ml). In the presence of methylprednisolone all concentrations of EGF increased fibronectin mRNA levels in a dose-dependent manner. It is concluded that EGF treatment can prevent the inhibitory effect of methylprednisolone on wound healing by stimulating fibroblast proliferation but does not stimulate collagen synthesis per cell.

Radical mastectomy wound as a model for studies of human wound metabolism.

Summary The nutritive aspects of human wounds were investigated in twelve patients who had undergone radical mastectomy for mammary cancer. Three days after surgery, the drains were removed and wound fluid was allowed to accumulate under the flaps. At certain intervals respiratory gas tensions, hydrogen ion concentration, buffering capacity, and lactate/pyruvate ratio were determined by aspiration of fluid filling the dead space of the wound. Between the fifth and fourteenth days after operation, the mean PO 2 increased from 14 mm Hg to 22 mm Hg whereas the mean PCO 2 , pH, and buffer base remained essentially unchanged. The lactate/pyruvate ratio decreased by 40 per cent during this period. Changes in the measured parameters became more prominent when plotted against the volume of the aspirated fluid (= dead space). Increases in fluid volume from 15 to 100 ml to over 300 ml was associated with a decrease in the mean PO 2 from 28 to 2 mm Hg and a 100 per cent increase in the lactate/pyruvate ratio. Changes in pH and PCO 2 values were inversely proportional with PCO 2 the greatest in large dead space wounds. Skin slough occurred once. In this wound, the PO 2 varied between 2 and 4 mm Hg, and the lactate/pyruvate ratio was extremely high. It is concluded that adequate oxygen supply and drainage are fundamental, and, to a great extent, rate-limiting for the healing of dead space wounds.

Effect of epidermal growth factor (EGF) on experimental granulation tissue

Subcutaneously implanted cylindrical hollow viscose cellulose sponges were used to study the effects of locally applied epidermal growth factor (EGF) on developing granulation tissue in rats. In the first set of experiments the test implants were treated with a single injection of a solution containing 5 micrograms of EGF in 0.5% albumin while the control implants were treated correspondingly with the carrier solution only. In the second set of experiments the injections of both test and control implants were repeated daily. Analyses of wound fluid and granulation tissue in the sponge cylinders were carried out 10 days after implantation. After single application of EGF no essential differences were detected in wound fluid prostaglandin E2 levels or various components of granulation tissue between the groups. After daily application, however, a stimulatory effect of EGF on granulation tissue formation was observed: cellularity increased, as evidenced by the elevated amounts of nucleic acids, and accumulation of collagen and glycosaminoglycans was enhanced.

Tissue oxygen tension in externally stabilized tibial fractures in rabbits during normal healing and infection

Permanently implanted Silastic tonometers were used to measure average extracellular oxygen tension in the medullary cavity of osteotomized rabbit tibias stabilized with external pin fixation. During uncomplicated healing the baseline bone pO2 rose slowly with time from 10 to 20 mm Hg while during staphylococcal infection pO2 varied between 8 and 15 mm Hg and showed no correlation with the healing time. The maximal response of the bone pO2 to oxygen breathing correlated linearly with the healing time whether the osteotomy was infected or not. On the 42nd day the maximal pO2 during systemic hyperoxia was 85 mm Hg for the control bones, 42 mm Hg for the osteotomized bones, and 30 mm Hg for the infected osteotomized bones. The results indicate moderate bone tissue hypoxia during uncomplicated healing and more profound hypoxia during healing affected by infection.